Thousands fled neighborhoods of Nigeria's largest city Monday during a third day of ethnic violence that witnesses said killed dozens, as fighters carrying machetes, swords, slingshots, bows and arrows vastly outnumbered police officers.

There are long-standing hostilities between the mainly Muslim Hausas and the Yorubas, most of whom are Christians and animists. The Hausas dominate Nigeria's north, while the Yorubas are the main tribe in the southwest.

The violence was the latest blow to the polluted and crime-ridden city of Lagos, which still is recovering from explosions at an army weapons depot that killed at least 1,000 people last week — many of them women and children who fell into a canal and drowned during a late-night stampede to escape the explosions.

Officials on Monday did not have a full count of the dead but witnesses said dozens of people were killed overnight in the streets of Idi Araba and Mushin, impoverished Lagos neighborhoods where the fighting between Yoruba and Hausa tribal fighters began Saturday.

In the morning, an Associated Press photographer saw a mob of Hausas hacking to death a suspected Yoruba militant with cutlasses and machetes. The body of another man was lying outside the area's main hospital bordering the two neighborhoods. Seventeen burned, mutilated bodies were counted by AP reporters Sunday.

Plumes of black smoke rose from several square miles of slums Monday, and fleeing witnesses said thousands of homes were razed. Gunshots reverberated through nearly abandoned streets. Elsewhere, streams of residents carried on their heads whatever belongings they could.

Some Hausa residents said members of a Yoruba militant group, Odudua, attacked Hausa homes and an Idi Araba mosque Saturday. The Yoruba fighters said the Hausas made the first move. Many others said the fighting began with a neighborhood squabble.

Hundreds of police moved in Sunday to impose a nighttime curfew.

But the violence resumed after midnight when some witnesses said Odudua members burned homes believed to be owned by Hausas, shot at residents and threw homemade petrol bombs. That could not be independently confirmed.

"We carried my grandmother from my house while they were shooting at us," said 30-year-old Mohammed Gorlunu, a fleeing Hausa resident. "My neighbor's house was burning when we left and maybe mine is burning now, too."

Police appeared to have retreated by Monday morning. The handful of remaining officers were vastly outnumbered by fighters toting machetes, swords, slingshots, bows and arrows.

"Only the army can stop this now. The police are not helping us any more," said Lateef Alawsa, a 35-year-old Hausa collecting glass bottles to make petrol bombs.

Africa's most populous country is riven with ethnic, religious and political divides. Thousands have been killed in periodic violence since President Olusegun Obasanjo won 1999 elections, ending 15 years of brutal military rule.

Although a former military officer, Obasanjo is a Yoruba and the army traditionally has been dominated by Hausas.

Thousands of people in the city of 12 million lost their homes in the explosions at the weapons depot. Authorities planned a mass burial of unclaimed bodies for Monday or Tuesday.